John Floyd Thomas Jr., 74, who Los Angeles police cold case detectives said was the notorious "Westside Rapist," pleaded guilty to the murders that took place in two waves, the first in Inglewood, Lennox and Los Angeles in the mid-1970s and the other in the Claremont-Pomona area a decade later.

The soft-spoken insurance claims specialist is described by the LAPD as one of the region's most prolific killers, responsible for as many as 30 slayings and about two dozen sexual assaults. But his plea in court Friday is for only seven killings.

The slayings involve Ethel Sokoloff, 68, in the Mid-Wilshire area in 1972; Elizabeth McKeown, 67, in Westchester in 1976; Cora Perry in Lennox in 1975; Maybelle Hudson, 80, Miriam McKinley, 65, and Evalyn Bunner, 56, all in 1976 in Inglewood.

The attacks appeared to stop in 1978, around the time Thomas was convicted and sentenced to state prison for the rape of a Pasadena woman. Thomas’ extensive criminal record also included serving a six-year state prison sentence, beginning in 1957, for burglary and attempted burglary. Two parole violations sent him back behind bars until 1966.

After his release in 1983, Thomas moved to Chino, which coincided with a wave of rapes and killings that began in the Pomona Valley area. Over the next six years, Los Angeles County sheriff's detectives would investigate five slayings of older women in Claremont, according to sources familiar with the investigation.

Adrienne Askew, 56, the last homicide with which Thomas was charged, was found strangled in 1986 in her Claremont apartment.

The killings appeared to stop in 1989, the same year Thomas took a job in the state workers' compensation agency in Glendale.

The Westside Rapist faded from public memory and authorities made limited progress in the Claremont killings until late 2001, when the LAPD created the Cold Case Homicide Unit that reopened about 9,000 unsolved slayings going back to 1960, using emerging state and federal DNA databases.

In September 2004, the department's crime lab matched male DNA taken from the McKeown and Sokoloff crime scenes but were unable to match it to a suspect. Over the next five years, detectives developed 14 suspects only to rule out each of them as the attacker.

The break came in October 2008, when two officers collected DNA from Thomas while searching for the so-called Grim Sleeper serial killing suspect. Nearly two years later, LAPD Robbery-Homicide detectives arrested Lonnie Franklin Jr. in connection with 10 slayings of women in South Los Angeles after identifying him using familial DNA.

In March 2009, the California Department of Justice DNA laboratory notified detectives that Thomas' DNA matched the evidence from the Sokoloff slaying. Within days, the lab matched Thomas' DNA to four other slayings, leading to his arrest.

Thomas was born in Los Angeles. His mother died when he was 12 and he was raised by his aunt and a godmother. Thomas attended public schools, including Manual Arts High School. He also served in the military.

He briefly joined the U.S. Air Force in 1956. At Nellis Air Force Base in Nevada, a superior described Thomas as often late and slovenly. He received a dishonorable discharge, according to his military records. The next year he was convicted of burglary and attempted burglary, which would land him behind bars for nearly a decade.

But it was just the start of the criminal career of the alleged "Westside Rapist," who became one of the more notorious criminals of the era, targeting victims who ranged in age from their 50s to their 90s, according to LAPD detectives.

Bella Stumbo, the late Times feature writer, wrote in December 1975 that the "serenity" of the neighborhoods where the victims lived had been “grotesquely invaded by that elusive maniac the police loosely refer to as the 'Westside rapist,' now accused of sexually assaulting at least 33 old women and murdering perhaps 10 of them." She said residents lived in "small colonies of terror."